Syrups containing methyl methacrylate as a principal component monomer are being used in the molding of glass-fiber-reinforced plates, kitchen counter tops, washstand tops and the like, and these molded articles have very excellent performance from the viewpoint of weather resistance in that they show no tendency to yellowing. However, conventional syrups must be molded by means of pressure molding equipment because they tend to shrink during the curing process. Moreover, where they are molded in a state containing such fillers as glass fibers, silica sand, alumina and the like, the molded articles so formed have the disadvantage that a loss of gloss, whitening and the like may occur as a result of use under severe conditions such as immersion in boiling water for a long period of time.
In order to overcome the above-described disadvantages, the present inventors previously completed an invention as described below and in U.S. Pat. No. 4,617,367. According to such invention, a methyl methacrylate syrup composition comprises an intimate mixture of 1-99 parts by weight of a first polymer-in-monomer syrup (A) and 99-1 parts by weight of a second polymer-in-monomer syrup which can be either (B.sub.1) or (B.sub.2), wherein the syrups (A), (B.sub.1) and (B.sub.2) are as follows:
(A) a polymer-in-monomer syrup obtained by copolymerizing a mixture of methyl methacrylate monomer, one or more monomers having reactivity with glycidyl groups and containing at least one ethylenically-unsaturated bond, and one or more of (meth)acrylates, styrene and styrene derivatives.
(B.sub.1) a polymer-in-monomer syrup obtained by copolymerizing a mixture of one or more monomers containing at least one glycidyl group and at least one ethylenically-unsaturated bond, and one or more monomers selected from the group consisting of methyl methacrylate, (meth)acrylates, styrene and styrene derivatives; and
(B.sub.2) a polymer-in-monomer syrup containing a copolymer obtained by copolymerizing one or more monomers containing at least one glycidyl group and one or more other copolymerizable monomers, having a number average molecular weight of 1,500-50,000 and containing a glycidyl group, in one or more monomers selected from the group consisting of methyl methacrylate and (meth)acrylates, styrene and styrene derivatives.
The aforesaid composition can be molded and cured under atmospheric pressure. The molded articles so formed have not only excellent weather resistance but also especially excellent water resistance, so that they do not suffer a loss of gloss, whitening or the like upon exposure to severe conditions such as immersion in boiling water for a long period of time.
However, the molded articles made of the aforesaid composition do not have satisfactorily high impact resistance. Moreover, when they are cut with a cutter into products having desired size and shape, cracks are often produced in the cut surfaces. Thus, there is a strong demand for a syrup composition capable of overcoming these disadvantages.